Big hats go on display during Ladies’ Day at the Grand National last month. Photograph: Tom Jenkins

The debacle on the red carpet at the Cannes film festival last week – where women were turned away from the gala screening of Todd Haynes’s Carol for not wearing high-heeled shoes – was rightly hailed as sexist dress-code policy.

It’s 2015. We are the most liberal generation ever – and yet we cling to anachronistic dress codes (written and unwritten) to help us navigate bewildering social events from white tie dinners to fetish clubs. And we’ve all suffered the fancy dress party where the zero-size hostess wants us all in bikinis.

According to clothing historian Philippa Stockley, snobbery is often confused with class, but good taste can never be mistaken. “At a themed costume party it depends on how intelligent and creative the host is. If the party is properly inclusive, guests could either wear an amazing bespoke outfit or just a feather in their hair. A good host never embarrasses a guest.”

Is it tyrannical fashion policing, or enjoyably bonkers ritual? You decide.

1 Ladies’ Day at Royal Ascot has long tried to uphold a “sartorial” dress code (to keep the oligarch wives and Wags in check), with helpful advice about dangling bra straps and the importance of wearing knickers. This year it even produced an extraordinary fashion video, showing us proles how to dress for the Royal Enclosure (dress straps an inch deep, headpieces must have a base of 4 inches, no midriffs, etc). Gentlemen are merely required to wear black or grey morning dress with a top hat. So they just look like mad penguins.

2 Invitations to the Queen’s garden party at Buckingham Palace tactfully suggest that for women the best attire is “day dress with hat or uniform (no medals)”, with the camp addition: “Trouser suits may be worn.” Social anthropologist Kate Fox argues in her book, Watching the English, that these “stage English” items of clothing – hats, waistcoats, veils and fascinators – bear no relationship to fashion. It’s about tribalism, conformity, a uniform. The only person truly allowed to be eccentric is the Queen, who continues to wear the same highly idiosyncratic style of clothing (a modified 50s retro look) with no regard to anyone else’s opinion.

Plunging sales has led Abercrombie & Fitch to ditch the ‘beefcakes’ who greet customers at stores. Photograph: Alamy

3 Posh boys just adore fancy dress, and at Oxford’s hell-raising Bullingdon Club grown men fight for the right to wear the ludicrous dickie-bowed uniform (navy tailcoat with a matching velvet collar, mustard waistcoat), available from the Oxford branch of Ede & Ravenscroft, robe makers to the Queen, at £3,000 a pop. A 1988 photo of David Cameron posing in his Bullingdon Club finery, alongside a baby-faced Boris Johnson, is on proud display in the Ede & Ravenscroft toilet.

4“Leggings are NOT pants,” insists Qatar, which has launched a social media campaign urging tourists to dress “modestly” in advance of 2022’s World Cup. Short dresses and crop tops are banned, while men wearing shorts and singlets in public will be frowned upon. “The amount of immodest clothing is growing in public places, especially shopping malls,” thunders Nasser al-Maliki, PR for the Qatar Islamic Cultural Center.

5 Never mind the high heels, it was only two years ago that Paris women were “allowed” to wear trousers, when the government overturned a 200-year-old ban where women needed to have the permission of local police if they wanted to “dress like a man” (a weasel way to prevent women doing certain jobs). The French insist the law was modified in 1892 and 1909 to allow women to wear trousers if they were “holding a bicycle handlebar or the reins of a horse”. So that’s all right then.

6 Preppy fashion brand Abercrombie & Fitch recently announced it is dropping its “look policy” – employing only the young, cool and slim. The strict dress code issued to staff includes advice on dying hair, cuffing jeans and scrunching sleeves. Plunging sales has led the company to also ditch the famous shirtless models (known as “beefcakes”) who greet customers at stores.